As I was sitting at my desk last week, I saw a little brown spider come out from behind some books. I suspected the spider was a brown recluse so I used a pencil to pin down its legs while looking for an insect box to put it in. Two of its legs fell off and started twitching, continuing for over two minutes while I got my camera to take this video.
Few spiders can be identified down to species just by their markings. Even black widows have several species, separated by the details of their hourglass. The identification of the brown recluse, aka fiddle spider, is "confirmed" by the fiddle marking on the dorsal thorax above. At least, that is what we were all taught.
this chart. For those of us non-arachnologists, looking one in the eye involves either a smashed spider or a camera. In this case it was this postmortem view that put it in the Loxosceles genera, called the brown spiders. There are eleven species of Loxosceles in the United States, but only Loxosceles reclusa is reported in Missouri.
|Exposed "hip joints"|
Opioliones actually have muscles in the trochanter that contract to prevent bleeding. "Two pacemaker nerve ganglia within the leg are activated as soon as communication with the central nervous system is severed. They operate independently, causing the leg to twitch and jerk. The legs even have their own trachae which supply the disembodied legs with oxygen. The leg can twitch for up to an hour, as opposed to 40 seconds without oxygen."*
I can't find any information on brown recluse spiders having disconnected twitching legs but I have the video and seeing is usually believing.
* Amazing Arachnids, Jillian Cowles.